The weakest form of light that is dangerous to humans is ultraviolet

View the electromagnetic spectrum and the properties of different types of light

All forms of electromagnetic radiation, from radio waves to gamma rays, travel at the speed of light in a vacuum, but their wavelengths decrease as their frequencies increase. The light-sensitive nerve cells in the human eye are sensitive to a narrow range of values, which we observe as the spectrum of visible light.

The ultraviolet catastrophe is the infinite energy prediction of classical physics

When scientists first tried calculating the radiation emitted by a heated object, their assumption was that energy was equally distributed across wavelengths and produced infinite energy at low wavelengths. This contradicted observations, which showed near-zero energy intensity at those values.

Infrared light is most often associated with thermal radiation and cooking food

Although extensively used in remote controls for electronics, where LED lights send signals wirelessly, infrared cameras allow for night vision and thermography—imaging of heat patterns in the body to non-invasively reveal blood flow for supplementary diagnostics. Infrared radiation also provides heat in toasters, saunas, and other technologies.

Why Earth would become a more deadly environment without the ozone layer

The ozone layer blocks almost all of the sun's harmful, including dangerous UVC rays that can damage cells by breaking chemical bonds. Without it, rates of skin cancer, crop failures, oceanic die-offs, and widespread ecosystem collapse would increase significantly, making Earth largely uninhabitable.

'Magic ink' is redefining the tattoo

One University of Colorado professor has developed an ink that can be "turned on" with exposure to UV light, and "turned off" with sunlight. While the ink could help those who want to hide their body art from family members or coworkers, there are potential uses for medical procedures.

Microchip fabricators create light by heating tin droplets to over 220,000 Kelvin

Every second, lasers strike 50,000 droplets moving at 250 kilometers (155 miles) per hour, vaporizing the tin in supernova-like miniature explosions that produce ultraviolet light. Knowing this light will spread via diffraction as it passes through a filter during manufacturing, designers reverse-engineer the filter design based on the required final microchip pattern.

Photographer captures glowing flowers in ultraviolet light

Debora Lombardi utilizes ultraviolet light to reveal unseen colors in flowers, re-shaping their natural beauty. Beginning during the lockdown of March 2020, Lombardi's experimentation evolved, culminating in a series recognized by the World Photography Organization. Her work highlights vibrant purples, blues, and yellows, transforming flowers into surreal, otherworldly specimens by exposing them to UV light in her Italy-based studio.

Light can be used to slow the motion of atoms

While photons possess energy, they also have momentum, which allows them to collide with other particles, much like billiard balls, thereby slowing them down and reducing their kinetic energy, or temperature. Using multiple lasers from different directions, particles can be cooled to within one degree of absolute zero.

Concentrated sound waves can collapse microscopic bubbles, creating light

The phenomenon, known as sonoluminescence, can generate extremely short, high-intensity flashes from the sudden focusing of sound energy, which can drive the temperature within the bubbles to values over twice that of the sun's surface.

A list of five everyday products that rely on radioactivity, including exit signs and gemstones

Like some glow-in-the-dark wristwatches, some exit signs contain sealed tubes of tritium—radioactive hydrogen gas—which emit low-energy beta particles that react with surrounding elements to produce light, making them visible without batteries. In smoke detectors, smoke particles disrupt the steady flow of ions generated by americium-241.

The UV index measures the sun's ultraviolet radiation risk on a scale of 1 to 11+

The tool takes into account geographical location, time, elevation, and cloud coverage to help individuals plan their daily activities around the sun's peak UV exposure times, which occur from 10:00 am to 4:00 pm. A value at or above 6 requires sunscreen (SPF 15+), shelter, or UPF clothing

Fluorescent bulbs can be illuminated by overhead power lines without making contact

The electromagnetic fields produced by the alternating current in transmission lines can induce the motion of charges in nearby objects. This motion yields electric currents that can light up bulbs but are too small to harm humans.

Microwave ovens heat food by agitating certain molecules with non-ionizing light

Molecules with resonant frequencies within the microwave range vibrate, producing heat between adjacent matter, just as hands warm when rubbed together. The mesh in front of an oven's door confines the microwaves to the container, while the rotating plate allows different parts of food to travel through regions of maximum vibration.

An explanation of the weak nuclear force, which can induce some forms of radioactive decay

While the strong nuclear force holds the protons and neutrons together in an atomic nucleus, despite the electromagnetic force pushing protons apart, the weak nuclear force can change the identity, or flavor, of the quarks that make up these particles. In doing so, protons can be converted into neutrons, and vice versa, altering the stability of atomic nuclei.

Explore 3D models of some of the most dangerous viruses

Everyone has come in contact with common viruses—typically something like influenza (the common flu)—but sometimes they encounter more dangerous strains. While we're familiar with the symptoms that manifest, it wasn't until the advent of advanced microscopy that scientists could pin down the exact structure and behavior of various viruses.

Ultrasound machines emit and collect high-frequency sound waves to construct images

Before its use in medical imaging, the technology was employed in World War I for submarine detection, the same way bats use sound for echolocation of obstacles. Differences in the penetrating power of different frequencies allow medical professionals to detect different structures in the body.

Bright blue fireworks are the most difficult color to create

Copper chloride emits blue light when heated, but breaks down at the temperatures created when fireworks explode. Pyrotechnicians continue to search for an ideal mixture that provides a temperature high enough for copper chloride to shine brightly without being destroyed.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

The origin of LASIK eye surgery, from a lab incident to federal funding and widespread use

After a University of Michigan engineering student suffered retinal burns from an ultrashort pulse laser, researchers realized it could be used to reshape the cornea and improve a person's vision with greater precision than a scalpel and earlier laser technologies. Agencies, including the National Science Foundation, the National Institutes of Health, and the Department of Energy, provided funding to develop and commercialize the procedure.

The chlorophyll in plants captures energy in the form of red and blue light

Light-dependent reactions during photosynthesis convert sunlight into chemical energy, stored within the bonds of molecules such as ATP and NADPH. Rather than being absorbed for these reactions, most green light is reflected, causing most plants to appear green.

Acrylamide forms naturally during high-heat cooking through the Maillard reaction

While studies have shown it can damage DNA and potentially cause cancer in mice, humans absorb and metabolize acrylamide at different rates, introducing uncertainty in the research's applicability to humans. Some international health agencies have nonetheless recommended avoiding darker roasts when cooking starchy foods.

Wood that changed the color of water was the earliest recorded example of fluorescence

Lignum nephriticum, a tea used to treat kidney and urinary illnesses, was described in the 16th century as derived from white wood that turned water a bluish hue. However, in the 17th century, accounts described the wood as reddish and creating a kaleidoscope of colors in water. In 1915, the sources were identified as two different woods, which absorb UV radiation and emit visible light.

Gamma Knife surgery uses incredibly precise, high-energy light to treat patients

A form of brain stereotactic radiosurgery, this non-invasive technology concentrates beams of light onto specific tumors to damage the DNA of malignant cells, killing them. The gamma rays used are in the same part of the electromagnetic spectrum as those produced in nuclear reactions, cosmic ray collisions, and radioactive decay.

Ultraprocessed foods include preservatives, dyes, sweeteners, and more

Processed foods are those that have been altered from their original state, which includes numerous processes that we consider natural, such as cooking or salting. Ultraprocessed foods contain at least one item that wouldn’t be found in a kitchen, like hydrogenated oils or high-fructose corn syrup. It’s estimated that nearly 75% of all foods consumed in the US are ultraprocessed, though that doesn’t mean that all of them are unhealthy. In fact, some, such as prepackaged whole wheat bread and soy milk, are recognized for their health benefits.

Particles found in Martian air pose significant risks to human lungs

Ultrafine dust, just 3 micrometers wide, is small enough to bypass lung defenses and enter the bloodstream, where its highly reactive chemicals can cause thyroid disease. Silica in the dust can also cause silicosis, a chronic and incurable lung disease.

Massive blooms of microscopic plankton called dinoflagellates produce the neon blue light seen in glowing tides.

Why bacterial bioremediation may help counter the negative effects of past chemical solutions

Molecules such as DDT, a synthetic insecticide, and PFAS—"forever" chemicals used to make products resistant to heat, water, and grease—have historically been used across various industries but are now known to be harmful. Microbes that can convert some of these substances into nontoxic products, such as water and carbon dioxide, have already been identified, with ongoing research to find others.

Firework or sparkler burns, even if they cover a relatively small area of skin, can significantly affect our range of motion.

Pure water does not conduct electricity because this flow of energy requires the movement of charged particles, and water is a neutral molecule.

The deadliest aspect of volcanic eruptions is often not lava, but pyroclastic flows—avalanches of ash, gas, and rock that can move more than half the speed of sound.

See how fireworks are made and learn how metals like magnesium and copper are responsible for different colors.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

Visualize how CRISPR-Cas9—a type of immune system used by single-celled organisms to attack invasive viruses—targets and makes precise changes to a gene's DNA.

All rainbows are 'raincircles' caused by water droplets separating white sunlight into a spectrum of colors, but Earth's surface blocks the bottom half of the circle from our line of sight.

Sunflowers have long been a symbol of nuclear disarmament because they can extract large amounts of radioactive cesium from soil.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

Marburg virus, related to Ebola, is also extremely deadly, and has no available vaccine.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

Tattoos remain visible on your skin thanks to immune cells called macrophages

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

This poison ivy knowledge quiz—accompanied by photos of the plant's varied forms—may help you identify this common rash-inducing growth.

A pickleball's loud 'pop' sound can reach 120 decibels, which is equivalent to a hammer hitting a nail

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in terms of casualties, forces mobilized, and displacement of civilians.

The Beatles' US label rejected the band's first two singles, 'Please Please Me' and 'From Me to You,' with one executive calling the band 'dead in the water.'

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.